Monday, August 20th

Prof. Yuichi Ikuhara

  • Institute of Engineering Innovation
    The University of Tokyo.
    Tokyo, Japan
    E-mail: ikuhara@sigma.t.u-tokyo.ac.jp

Biography

Yuichi Ikuhara is Professor and Director of Nanotechnology Center, Institute of Engineering Innovation at University of Tokyo since 2003. He received Dr.Eng. from Department of Materials Sciences, Kyushu University in 1988. His current research interest is in interface and grain boundary and interface phenomena, advanced transmission electron microscopy and so on. Dr.Ikuhara is author and coauthor of about 720 scientific original papers in this field, and has more than 350 invited talks at international and domestic conferences. He received“Medal with Purple Ribbon”from the Emperor of Japan (2016), “Humboldt Research Award”from Alexander von Humboldt Foundation (2010) and so on. He is a fellow of the American Ceramics Society (2011), member of World Ceramic Academy (2014), and an associate member of the Science Council of Japan. He holds a group leader position at JFCC (Japan Fine Ceramics Center) and WPI (World Premier International Research Center Initiative) professor at Tohoku University concurrently.

Abstract

Grain Boundary and Surface Dynamics in Ceramics

Many experimental investigations have been tried for understanding the dislocation-grain boundary interaction in materials, but these experiments were mostly carried out statically, and the dynamic behavior is still not well understood yet. It has been known that several oxide crystals can be plastically deformed even at R.T. by dislocation slip like metals. In this study, the in-situ nanoindentation experiments were conducted for SrTiO3 single crystal and its bicrystals inside TEM. For bicrystal experiments, various types of GBs including CSL (Coincidence Site Lattice) GBs and low angle tilt and twist GBs were prepared. Various interface phenomena such as dislocation pile-up at GBs, jog formation, jog-drag motion were dynamically observed. The dislocation-GB interaction and its dependence on the GB characters will be discussed in detail.

The properties of lithium ion battery (LIB) cathodes strongly depend on the diffusion of lithium ions during charge/discharge process. Then, direct visualization of lithium site is required to understand the mechanism of the diffusion of lithium ions. In this study, aberration corrected STEM were applied to directly observe the {010} surface, which coresponded to perpendular to the 1-D diffusion orientation, of the olivine LixFePO4. It was found that orientation of boundary layers at the FePO4/Li2/3FePO4 interface gradually changed from lower index planes to higher index planes. The mechanism of the lithiation/delithiation from and to the surface will be discussed based on the observation results.